This invention relates to steerable axle assemblies of the type utilizing kingpins for securement of steering knuckles to steering axle bosses. More particularly, this invention relates to apparatus designed to retain a kingpin against rotational movement within an axle boss, notwithstanding wear during the useful life of the kingpin.
In conventional front suspension systems for highway vehicles such as trucks, wheel spindles are connected to a front axles through steering knuckle and kingpin members. Typically, the knuckle has a bifurcated yoke for coupling the knuckle to a fixed axle boss, and the kingpin extends through aligned apertures in the yoke and a bore in the axle boss to retain the members together. The normally vertically oriented axle boss, designed to support the steering knuckle, is an integral part of the front axle. The knuckle is adapted to pivot about the kingpin on a vertical steering axis.
The axle boss, also called a knuckle support boss, thus non-rotatably retains the kingpin but permits rotation of the knuckle. A roller bearing mounted between the knuckle support and the lower arm of the bifurcated yoke permits low frictional movement of the knuckle about the steering axis. The upper arm generally supports a bushing for accommodating a lesser load.
Due to manufacturing tolerances, the kingpin roller bearing and bushing are often not precisely fitted between lower and upper arms of the knuckle yoke. The resulting gaps or clearances allow the members to shift relative to one another, particularly as a result of wear over the useful life of the parts. In heavy duty truck suspension systems, kingpins are normally secured against rotation by means of drawkeys having tapered surfaces drawn against the sides of the kingpins. However, as a result of wear, greater clearances are created, permitting the kingpins to shift and oscillate within their associated knuckle bores during the useful lives of the parts. Such movement exacerbates the wear problem.